CODEWITHSUNDEEP
r
Peter
Peter

Reputation: 393

R - Set execution time limit in loop

I have a script that uses the rNOMADS package to download forecast data. Currently, it uses a for loop to call the forecast download function for each three hour forecast interval in order. The issue is the download function occasionally "freezes" at random which forces me to terminate R and start the process over. When it freezes the code hangs at the download function for minutes instead of the typical <1 sec it takes to execute, and then when I try to halt execution I get a message saying "R is not resrponding to your request to interrupt processing so to stop the current operation you may need to terminate R entirely."

Is there a way set a time limit for a specific block of code to execute in each for loop iteration, and then skip that block of code and throw an error if the time limit is reached? Something like tryCatch, that I could use to raise a flag to re-do that for loop iteration?

Something like:

for (i in 1:N) {
   ...

   setTimeLimit(XXX seconds) {
      downloadFunction()
   } timeLimitReached {
      doOverFlag <- 1
   }
}

Thanks in advance!

Upvotes: 13

Views: 7599

Answers (4)

ADIT
ADIT

Reputation: 1

Good advice, following on from the answers above, and regarding the fact that the loop stops: To avoid breaking the entire loop, make sure you add if (all(class(variable_name)=="try-error")) next()

Upvotes: 0

Brandon Bertelsen
Brandon Bertelsen

Reputation: 44648

I really like R.utils for some situations, but it clobbers the traceback for the internal error message if there was one (lets' say you're running in parallel and want to wrap it in a timeout)

R base has the functionality setTimeLimit that you can wrap using {} with your expression. It returns a simple error message so it's very useful and does not remove other error handling possibilities (like withCallingHandlers which is extremely useful for parsing/storing error messages and the call stack): 

test_fun <- function() { 
  repeat {
    runif(100)
  }
}

res <- { 
  setTimeLimit(5)
  test_fun()
}

Upvotes: 9

Alexander Borochkin
Alexander Borochkin

Reputation: 4621

This function works as follows now:

library(R.utils)
withTimeout(Sys.sleep(10), timeout = 1)#stop execution after one second

Upvotes: 4

kasterma
kasterma

Reputation: 4469

The function evalWithTimeout of package R.utils does this.

evalWithTimeout(Sys.sleep(10), timeout = 1)

(times are in seconds).

Note: I have not used this function a lot, I liked your question so I did some googling around and found this.

Upvotes: 17

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